Flexor tendon injuries affecting hand function are common in young adults, and frequently result in significant disability. Adhesion formation continues to be a difficult problem, which leads a poor outcome after flexor tendon repairs. The tendon graft still plays a very important role in reconstruction to restore finger function, either to replace a damaged tendon or to lengthen a healthy tendon for transfer. Clinically, although most tendon grafts go into a synovial environment i.e., a tendon system that includes a synovially lined sheath, most tendon grafts come from extrasynovial tendon sources. Animal models have shown that extrasynovial tendon grafts are associated with more adhesions to the surrounding tissue than intrasynovial tendon grafts. In the previously pilot study, we found that extrasynovial tendon has a rough surface and higher gliding resistance compared to intrasynovial tendon. Although friction can be reduced with the application of hyaluronic acid (HA) applied to the tendon surface, its effect is diminished after repetitive motion because of weak binding between HA and the tendon surface. Furthermore, the half-life of HA in tissues is short. We have found that carbodiimide derivatization of HA (cd-HA) gelatin enhances the binding ability of HA to the tendon surface, decreases the friction, and increase the half-life of HA in tissues in vitro. We hypothesize that cd-HA gelatin can improve the gliding ability and the abrasion effect of tendon grafts in vivo, and thereby decreasing adhesion formation. In order to test this hypothesis, the following specific aims are proposed: 1) To identify and quantify the surface status of extrasynovial tendon modified by cd-HA gelatin in vitro, 2) To identify the gliding characteristics, adhesion formation, and healing status in vivo after tendon grafting with an extrasynovial tendon treated by the cd-HA gelatin. If the hypothesis is supported, future studies can investigate the mechanisms by which this effect on tendon graft gliding and adhesions is achieved, and the use of cd-HA gelatin as a vehicle to carry anti-inflammatory or growth factors to the tendon surface, to improve the quality of tendon graft healing.